Synchro exciter



Jan. 8, 1952 C. W. SHERWIN SYNCHRO EXCITER Filed April 16. 1946 l NVENTOR CHALMERS W. SHERWIN ATTORNEY Patented Jan. 8, 1952 SYNCHRO EXCITER Chalmers W. Sherwin, Leonia, N. J., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application April 16, 1946, Serial No. 662,463

4 Claims.

This invention relates to synchro systems and more specifically to a method of exciting a synchro with an alternating current signal.

In many applications it is desirable to excite a synchro with an alternating current signal in the audible frequency range. This may be done most efliciently by making the synchro rotor part of a circuit resonant at the desired frequency. The resonant circuit, including the synchro rotor, may then be used as the tank circuit of an electron tube oscillator.

The object of this invention is to provide an efficient system for exciting a synchro with an alternating current.

Another object is to provide a synchro exciting system whereby the synchro rotor is part of a resonant circuit.

A further object is to provide an electron tube oscillator using a synchro rotor as part of the resonant circuit.

These and other objects will be apparent from the following specification when considered with the accompanying drawing, the single figure of which shows a schematic diagram of an embodiment of the invention.

Referring to the accompany drawing, a conventional synchro is shown composed of the stator windings Ill and rotor winding II. Output of the synchro is taken at terminals I2. A capacitor I3 forms a parallel resonant circuit with rotor winding II. The plate of an electron tube I4 is connected through the parallel combination of the rotor winding I I and capacitor I3 to a source of plate potential 3+. The cathode of tube l4 connects to ground. A capacitor I5 couples from the plate of tube I4 to the grid of a second electron tube I6. The grid of tube I 6 connects to ground through a resistor I1 and the cathode of tube It is grounded. A resistor I8 connects from the plate of tube l6 to the source of plate potential B+. Capacitor I9 couples from the plate of tube It to the grid of tube I4. Resistor 20 connects from the grid of tube I4 to ground.

In operation, the parallel combination of capacitor I3 and the rotor winding II form the resonant circut of an electron tube oscillator. Tube I4 is the oscillator tube and tube I6 and the associated circuit form the feedback circuit for the oscillator. The signal at the plate of tube It is coupled to the grid of tube I6 by capacitor I5. This signal is amplified by tube I6 and is reversed in phase. The signal at the plate of tube It is coupled to the grid of tube I4 by capacitor I9. Thus the signal at the grid of tube I4 is of 2 the opposite phase to the signal at the plate of tube I4. This condition will cause oscillation to occur at the resonant frequency of the circuit formed by rotor II and capacitor I3. Thus the rotor winding I I will be excited with an alternating current.

The frequency of the oscillation may be controlled by variation of capacitor I3. The frequency of the oscillation will be reasonably constant as the inductance of rotor winding II does not change appreciably as it is rotated. If the rotor II is of the type known as distributed wound, the change in inductance with angle of rotation is very small.

Other forms of oscillators may be used. For example, a transformer may be used to provide the feedback or a Colpitts type of oscillator may be constructed using the rotor winding I I as the inductance. The novel features of the invention include; the excitation of a synchro by resonating the excited rotor by a parallel capacitor at the frequency of the exciting alternating current, and the inclusion of the excited rotor as an element of the resonant circuit of an electron tube oscillator.

While a particular embodiment of the invention has been illustrated and described, it is to be understood that the invention is not to be limited thereby in its details of construction and operation, except as appears hereafter in the claims.

What is claimed is:

1. An excitation circuit for a synchro having a rotatable rotor coil comprising, an oscillator having a tank capacitance, and means connecting said rotor coil in shunt with said capacitance, whereby said rotor coil comprises the tank inductance of said oscillator.

2. Apparatus for exciting angular motion transmission apparatus having relatively rotatable primary and secondary windings comprising, an oscillator energized from a direct current source and having a tank capacitance, and means connecting said capacitance in shunt with said primary winding.

3. Apparatus for exciting angular motion transmission apparatus having relatively rotatable primary and secondary windings comprising, an electron tube oscillator including a source of direct current voltage source for energizing said oscillator and a frequency determining circuit including a tank capacitance, and means connecting said capacitance in shunt with said primary winding.

4. Apparatus for exciting angular motion transmission apparatus having relatively rotata- 2,582,208 S 3 4 v ble primary and secondary windings comprising, REFERENCES CITED an oscillator having a tank capacitance and a The following references are of record in the direct current energizing source, and means confile of this patent: necting said. capacitance in shunt with said primary winding whereby said primary winding 0p- 5 UNITED STATES PATENTS crates as the tank inductance of said oscillator. Number Name Date 416,006 Moennich Nov. 26, 1889 CHALMERS SHERWIN- 2,420,160 Adamson May 6, 194': 

